Dual Energy X-ray Absorptiometry
Bodycomp Imaging Vancouver uses a Hologic Discovery Wi densitometer. We are currently running Hologic APEX Software Version 3.3 Bodycomp White Rock uses a Hologic Horizon Wi.
The scanner measures the grams of lean tissue, fat and bone in your body while producing an x-ray type image of your body. The technologists use this image to measure the fat and lean mass in each of your limbs as well as the torso.
We can compare lean mass in your arms or legs to check for symmetry, as having one limb with greater lean mass than the other can predispose you to injury. We can also check the percent fat of your abdomen to ensure that it is equal to or less than your total body fat. Carrying excess fat in the abdominal region is associated with increased risk of heart disease, diabetes and some cancers.
The scan is not diagnostic for arthritic changes, fractures or tumors - it is not the same as an x-ray that you would have taken of a broken bone.
A DXA body composition scan is the gold standard in body fat testing. Skinfolds (calipers) and bioelectrical impedance, the tests commonly used in gyms, provide less accurate and less detailed information. We can provide you with the most accurate assessment of your body composition available.
While underwater weighing (UWW) was considered the most accurate method to assess percent body fat in the past, researchers, elite athletes and medical specialists have been using DXA for more than 15 years. DXA is a three compartment model, accounting for bone mass, lean mass and fat mass while UWW can only differentiate fat and non-fat tissue. Also, to obtain accurate values in UWW a subject’s residual lung volume must be measured. UWW requires a subject to sit very still on a scale while submersed underwater and to have expelled all the air form their lungs. The process is repeated three to ten times and the values are averaged. You can see why most clients prefer a DXA scan over UWW measurements.
As everyone’s starting point is different and their training/diet changes can vary there is no ideal time for re-measurement for everyone. It is usual to wait from between 3 and 6 months between scans to see meaningful results. If in doubt about when it’s time to be retested, contact us and tell us about your fitness/dietary changes and well help you decide when to get retested.
In small doses, there are no known negative side effects from x-rays. The radiation exposure in DXA is one of the lowest for medical tests. If you have any concerns regarding the radiation exposure, please talk with the technologist before proceeding with your scan.
Yes. While we ask our clients to be free of metal for the scan, any metal that is non-removable will be consistent from scan to scan and will not greatly influence the results. Unlike an MRI where metal objects can interact with the scan process, the x-ray beams used in DXA will be blocked by the metal object and so surrounding tissue will inaccurately be classified as bone, but it will be consistent from scan to scan.
While we get a value for the total bone mass in the body from a total body scan, it is not the ideal way of assessing fracture risk. Bodycomp Imaging offers bone density screening, where the hip and the spine are imaged in detail to assess your fracture risk. If you are interested in fracture assessment then contact us to discuss a bone density screening test.
While some of our clients are elite athletes and use our scan to tweak their training routine, the majority of our clients are average people. Some come to us for a baseline scan before embarking on a weight loss plan and then have follow-ups every three months to monitor their progress. Significant weight loss will usually results in some loss of lean tissue, but minimizing the amount of lean tissue lost and maximizing the amount of fat loss is ideal. Lean tissue is metabolically more active than fat so having a greater lean to fat ratio will result in an increased metabolic rate.
The DXA total body scan is accurate to 300 grams. The fat and lean components are accurate to 500 grams. A whole body scan percent fat value has about a 98.5 percent accuracy.
Two distinct x-ray energies pass through the tissues of the body and are blocked or attenuated relative to the density of the tissues they are penetrating. This allows the scanner to generate a map of the lean, fat and bone mineral content per pixel.
The DXA scan table has a weight limit of 350lbs. Unfortunately we are unable to scan clients who weigh more than this. The table top also has a length limit of 6’5”. In clients taller than 6’5” a portion of their head or feet will not be included in the scan area. However, these clients can still be scanned with good accuracy.
Casual work-out wear without zippers, studs or snaps is appropriate for scanning. For clients with metal on their clothing, we provide clean hospital style scrubs to change into.
We compare your percent fat values to data from the American College of Sports Medicine and give a classification of too little fat, fitness, healthy or obese. These classifications are designed to indicate health risks due to the quantity of body fat present. Clients are also encouraged to use their own scans to monitor their progress. A baseline scan compared to a scan taken three months later will allow the client to monitor the effectiveness of their workout and/or diet routines by the change in lean and fat tissue. It is also important to note that even a small reduction in percent fat can represent very real health benefits in obese individuals.
We are not an MSP insured service. The coverage of different health care plans vary considerably so you would have to check with your plan holder to determine if they will reimburse any or all of the scan fee.
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Interactive explanation of radiation via Baylor College of Medicine (click on the measuring radiation link at the bottom of the page)